1. Field of the Invention.
The invention, in general, relates to a method and an apparatus for mechanically processing of workpieces and for assembling and disassembling of structural units and, more particularly, to an apparatus in which workpieces to be processed, or structural units to be assembled or disassembled, as the case may be, are secured on an adjustable and, optionally, removable clamping tray of the kind integrated in such machine tools as, for instance, CNC-controlled grinding machines, milling machines, boring mills and the like, or utilized in transfer lines for assembling or disassembling structural units.
2. The State of the Art.
To reduce idle times during mechanical processing, assembly or disassembly operations, and to increase productivity and manufacturing capabilities, it is common practice to incorporate individual machine tools or even entire machine systems into assembly or disassembly lines. Proposals aimed at satisfying these requirements have not been lacking. They have been addressed to such operations as securing and releasing workpieces on workpiece clamping trays, aligning workpieces relative to processing tools, positioning workpieces for purposes of processing, as well as to motors accommodating such operations.
For instance, German patent DE 21 02 234 A1 relates to a drive for moving, within an assembly line, tool supports into predetermined positions in a transport path. To this end, a plurality of primary and secondary components of conventional linear motors is used cooperating alternatingly and by pulsed energization. The primary components are disposed in spaced relationship along a transport path, either singly or in groups. The secondary components are mounted on the tool support.
Grouped primary components are aligned either in parallel or angularly with respect to each other, and predetermined primary groups are connected in a consecutive sequence to a source of three-phase or direct current by means of switches actuated by the tool support. Each the secondary components consists of a plate of high magnetic conductivity and, when facing a primary component, and which is covered by an electrically highly conductive plate. Both secondary components are longer than any one of those primary components which are disposed in the same manner as they are.
Two parallel strips of high magnetic conductivity are embedded in the plate of high electric conductivity and extend laterally thereof. Each one of the strips is wider than the width of notches of the primary components and the center spacing between them which corresponds to the spacing between two opposite poles of the primary components.
In such an arrangement an air cushion is built up between the tool support and the transport path, and a conventional linear motor is utilized as a drive.
Clamping or lifting of workpieces by means of a magnetic clamping tray is known from European patent EP 0,357,904 A1 which describes a magnetic clamping tray capable of securely retaining not only workpieces made from different materials, but also workpieces made from weakly and non-magnetic materials. Its surface is structured such that it supports a workpiece in any position; at the same time it ensures appropriate vacuum pressure by an unimpeded air flow.
Two embodiments are described. In one embodiment slots or bores are formed in the magnetic pole sections between pole conduits which are made of non-ferromagnetic material and which are filled with a fine porous sintered metal.
In the other embodiment, the slots are provided in the pole conduits and are also filled with a fine porous sintered metal which in this case, however, is not ferromagnetic.
While it is possible magnetically to secure a workpiece with the described combination vacuum and magnetic clamping tray, it is not possible, for instance, to align or move a workpiece provided on the magnetic clamping tray.
Furthermore, German patent DE 196 28 921 A1 discloses a machine tool system for mechanical operation which consists of a machine base in operative connection with a gantry supported laterally of the foundation of the machine and extending over the machine base. The base of the machine is provided with a bed for receiving and supporting a clamping device. The receiving bed may be moved in the direction of the longitudinal or x-axis of the machine.
The receiving bed is provided with a clamping device which may be magnetically supported, arrested and positioned and which workpieces to be secured on the clamping tray. The entire clamping device may be magnetically lifted, moved and positioned. It may also be lowered and magnetically clamped, preferably by hybrid magnets, on the receiving bed.
It is also known to structure the clamping tray of such a clamping device for movement and adjustment not only along its x and y axes, but also for angular movements and adjustments about its vertical axis, by appropriate lifting and adjustment devices.
In these known arrangements,lifting magnets move the clamping devices with workpieces placed thereon are put into a floating state which state they may be adjusted, positioned and lowered to be secured by arresting magnets. With the clamping tray in this lowered and secured position, the workpieces may be subjected to defined processing operations.
It is an object of the invention to provide a method and an apparatus capable of performing mechanical processes and operations on workpieces and of assembling or disassembling, as the case may be, structural units, and of positioning workpieces or structural units placed on a clamping tray of a machine system relative to tool systems, assembly devices, processing systems and the like which are disposed on one or more gantries which extend over, or are arranged around, the clamping tray.